1. Field of the Invention
The invention relates to tank type vacuum cleaners and more particularly to the type of vacuum cleaner that is especially adapted to use in the home, in the workshop, and in industry as a wet or dry type vacuum and the primary object of the present invention is to provide an improved device of this character.
2. Description of Prior Art
The wet or dry shop vacuums presently in the marketplace characteristically consist of on open top collection tank mounted on wheels or casters and a cover or lid in which an electric motor and fan unit are mounted. The fan unit creates a suction within the tank and debris and liquid are drawn into the tank through a vacuum hose which is connected to an inlet located in the cover of the tank or to an inlet located high on the side of the tank itself. The air being drawn from the inside of the tank and through the fan is filtered to prevent dust and debris from reaching the motor and fan unit and to prevent dust and debris-laden exhaust from being expelled into the environment in which the vacuum is being operated. While filter methods vary, the most usual is a cylindrical filter of paper, cloth, or other porous material suspended from the cover of the tank and incorporating a check ball or float arrangement which cuts off suction to the fan unit should the liquid level in the tank rise to a level at which it threatens to enter the motor and fan unit itself. Caster mounts and casters located around the lower circumference of the tank give the vacuum cleaner mobility and the operator normally drags the vacuum assembly over the surface being vacuumed using the external vacuum hose as a tow line.
The advantages of the above described arrangements are apparent to anyone practiced in the art: (1) the fan and electric motor unit is relatively isolated from debris and especially from liquids coming into and being stored in the tank, (2) the arrangement readily lends itself to a filter and filter housing located below the motor and fan unit, attached to the cover, and containing a simple ball or float check valve, (3) the location of the inlet which connects to the vacuum hose in the cover of the assembly or at a point high up along the side of the tank makes it possible for a large amount of debris and liquid to accumulate in the tank before such accumulation reaches a level which would close off the vacuum inlet and (4) the location of the heavy operating machinery of the vacuum in and attached to the cover of the assembly makes for convenience and ease of emptying the tank inasmuch as the weight of the operating machinery is removed when the cover is removed.
The disadvantages of the above described arrangements are readily apparent to anyone who has ever actually used the wet or dry shop vacuums which are currently in the marketplace and fit the above description: (1) the location of the electric motor and fan unit at the top of the assembly creates a high center of gravity which results in extreme vertical instability for the entire assembly and (2) the location of the vacuum hose inlet in the cover at the top of the assembly or in the side of the tank a short distance down from the top of the tank causes the operator to exert substantial leverage on the inherently unstable assembly when the operator attempts to drag the vacuum forward using the vacuum hose as the tow line. When the casters or wheels on which the assembly is mounted encounter any debris or obstruction, or even such resistance as is offered by a thick pile carpet, and the operator attempts to pull the unit forward using the vacuum hose as a tow line, the combination of high center of gravity and substantial mechanical advantage produced by the high connection point for the vacuum hose conspire to cause the vacuum cleaner assembly to capsize.
The problem of extreme vertical instability created by the high center of gravity found in wet or dry vacuums now in the marketplace is solved in a novel and simple manner by the invention disclosed in my co-pending Application entitled "Wet or Dry Vacuum with Low Center of Gravity". The problem of substantial leverage produced by an external hose connection located high on a wet or dry vacuum assembly and the destabilizing effect of attempting to tow the assembly using the external vacuum hose as a tow line is dealt with and solved in a simple and novel manner by the present invention.
The degree of increased stability achieved by lowering the connection point for the external vacuum hose will vary from one vacuum assembly to another, depending upon the weight distribution and center of gravity of the assembly itself. The substantial decrease in mechanical advantage that comes with lowering the vacuum connection to the base of the assembly is apparent. The relationships between the parts are the relationships of the parts of a second class lever: the point on the floor at which resistance or an obstacle stops the forward motion of a caster being the fulcrum, the weight of the assembly concentrated at its center of gravity being the resisting force, and the forward pressure being applied to the external vacuum hose being the applied force. When the external vacuum hose is moved from a connection point at the top of the assembly, for example two feet above the fulcrum, to a point at the base of the assembly three or four inches from the fulcrum, the loss of mechanical advantage is such that approximately six times as much applied force is required to lift and capsize the assembly.